[POWERPC] axonram: Module modification for latest firmware API changes

Firmware would not deliver two interrupt numbers in device-tree any more
but only one, for correctable ECC, because uncorrectable ECC from now
is handled by firmware itself.
Changes in the axonram module are necessary because in the old version, if
it is not allowed to fetch the second interrupt number from device-tree,
it interpretes this as an error case and exits.

Signed-off-by: Maximilian <maxim@de.ibm.com>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>